The following terms and abbreviations are herewith defined, at least some of which are referred to within the following description of the prior art and the present invention.
BSS Base Station Subsystem
GGSN Gateway GPRS Support Node
GPRS General Packet Radio Service
GSM Global System for Mobile Communication
HLR Home Location Register
IP Internet Protocol
MS Mobile Station
PDN Packet Data Network
PDP Packet Data Protocol
PMM Packet Mobility Management
PS Packet Switched
QoS Quality of Service
RA Routing Area
RAI Routing Area Identify
RAU Routing Area Update
RAUP Routing Area Update Procedure
SGSN Serving GPRS Support Node
UE User Equipment
UMTS Universal Mobile Telecommunications System
UTRAN UMTS Terrestrial Radio Access Network
BSS: In a GSM network, the combination of the Base Station Transceiver (BTS) and the Base Station Controller (BSC).
GGSN: The GGSN is the gateway between a GPRS wireless network and an external packet data network (PDN) such as a radio network, an IP network, or a private network. In addition, the GGSN provides network access to an external host wishing to communicate with mobile subscribers/mobile stations.
PDP Context: A PDP Context is a logical association between a mobile station and a packet data network running across a GPRS network. It defines aspects such as routing, Quality of Service (QoS), Security, Billing etc.
SGSN: The SGSN mediates access to network resources on behalf of mobile subscribers/mobile stations and implements a packet scheduling policy between different QoS classes. In addition, the SGSN is responsible for establishing a PDP context with the GGSN upon activation.
UTRAN: UMTS Terrestrial Radio Access Network. It is the part of the UMTS network that consists of the Radio Network Controllers and their associated Node Bs. It is analogous to the BSS in GSM networks.
In military, civil defense or disaster recovery operations, it is often advantageous to deploy a portable “network-in-a-box” system which is a scaled-down communication system. The scaled-down communication system provides one or more wireless services (e.g., UMTS and GSM services) to mobile stations that are located within its radio coverage area without being dependent on the physical connectivity to any other telecommunications infrastructure. The scaled-down communication system, also referred to as a compact system, contains core network components including, for example, the GGSN, the SGSN, the UTRAN and the BSS.
If a number of such compact systems are deployed, with an IP host providing communication between the individual compact systems, then it is possible for the mobile stations being served by these compact systems to roam from one compact system to another compact system. FIG. 1 (PRIOR ART) is a block diagram of a communication system 100 which has an IP host 110 that interfaces with an IP network 115 which enables communications between two compact systems 120 and 130 (note: two compact systems 120 and 130 have been shown but in practice any number of such compact systems can actually be deployed). The first compact system 120 has core network components including a GGSN 122, a SGSN 124, a UTRAN 126 and a BSS 128. Likewise, the second compact system 130 has core network components including a GGSN 132, a SGSN 134, a UTRAN 136 and a BSS 138. In this set-up, it is possible for mobile stations 140a, 140b and 140c (e.g., GSM MS 140a and UEs 140b and 140c) being served by the first compact system 120 (or second compact system 130) to roam to the second compact system 130 (or first compact system 120) (note: the GSM MS 140a would be serviced by the BSS 128 and the UEs 140b and 140c would be serviced by the UTRAN 126). To enable this roaming feature, the communication system 100 is configured where each compact system 120 and 130 has a unique routing area (RA) so that the mobile stations 140a, 140b and 140c attachment to the compact systems 120 and 130 is known at the granularity of one compact system 120 and 130.
In this communication system 100, assume the mobile station 140b (for example) is attached to the first compact system 120 and receiving packets 145a from the IP host 110 via the IP network 115, the GGSN 122, the SGSN 124 and the UTRAN 126. Then, assume the mobile station 140b roams from the radio coverage area of the first compact system 120 into the radio coverage area of the second compact system 130. At this point, the mobile station 140b initiates an inter-SGSN RAU operation which causes the PDP context of the mobile station 140b to be moved from the old SGSN 124 to the new SGSN 134. Then, the new SGSN 134 informs the old GGSN 122 that the attachment point of the mobile station 140b to the network has changed and henceforth packets 145b addressed to the mobile station 140b are to be routed to the new SGSN 134 and not the old SGSN 124.
This particular routing of the packets 145b from the originating IP host 110 over the IP network 115 to the GGSN 122 in the first compact system 120 and then out again over the IP network 115 to the SGSN 134 in the second compact system 130 before being delivered to the mobile station 140b is not desirable. Because, the “tromboning” of the packets 145b wastes bandwidth on the inter-system IP network 115 and adds to packet latency. Plus, when the mobile station 140b is being served by the second compact system 130 it is also dependent on the proper functioning of the GGSN 122 in the first compact system 120. This situation is not desirable because the mobile station 140b is now dependent on the proper functioning of two compact systems 120 and 130. Accordingly, there has been and is a need to address these shortcomings and other shortcomings that are associated with the traditional communication system 100. This particular need and other needs are addressed by the present invention.